5,323 research outputs found

    New revision underway: American beetles : a handbook of the beetles of Nearctic America

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    Several Coleopterists have been asked to revise the family sections, working from diskettes modified and provided from the original "Beetles of the United States." They will rewrite these sections, and will be recognized as the author of the section. They are asked to sign a writing contract with the publisher. Other Coleopterists have been asked to review the family sections of the new book. These persons are acknowledged in the family section text

    Synergies

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    Identification of weta foraging on brodifacoum bait and the risk of secondary poisoning for birds on Quail Island, Canterbury, New Zealand

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    Brodifacoum is a second-generation anticoagulant used for rodent control in New Zealand. Concerns about the poisoning of non-target species have resulted in restrictions being imposed on the mainland. It is, however, still commonly employed on offshore islands. Previous research investigating the poisoning risks of brodifacoum has generally focused on birds eating brodifacoum bait (primary poisoning) or through depredation of live rodents or carrion containing brodifacoum residues (secondary poisoning). Other research has highlighted the potential for secondary poisoning of birds via the consumption of contaminated invertebrates. An inspection of rodent bait stations undertaken on Quail Island revealed that both cave and ground weta were feeding on brodifacoum bait. A sample of ground weta (Hemiandrus n. sp.) and cave weta (Pleioplectron simplex) was removed from Quail Island and exposed to toxic bait for 60 days. These weta were then assayed for brodifacoum residues and the values used to quantify the secondary poisoning risk for bird species found around Quail Island. We also calculated the risk to birds of secondary poisoning from the tree weta (Hemideina ricta) and the risk of primary poisoning via direct consumption of brodifacoum bait. The LD50 estimates indicated a low risk of secondary poisoning from contaminated ground weta and cave weta. By contrast, the estimates indicated a higher risk from larger-bodied tree weta; however, our calculations were based on a single residue concentration value and should be treated with caution. Of most concern was the primary poisoning risk from the brodifacoum bait. The results indicated that all the 17 bird species assessed are more susceptible to primary poisoning than secondary poisoning and access to brodifacoum bait by non-target bird species needs to be minimised

    Simplification or elaboration? The Effects of Two Types of Text Modifications on Foreign Language Reading Comprehension

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    Linguistic simplification of written texts can increase their comprehensibility for non-native speakers, but reduce their utility for language learning in other ways, e.g. through the removal of linguistic items that learners do not know but need to learn. A study was conducted to test the hypothesis that some elaborative modifications observed in oral foreigner talk discourse, where redundancy and explicitness compensate for unknown linguistic items, offer a potential alternative approach to written text modification. 13 reading passages were presented to 483 Japanese college students in one of three forms: native baseline, simplified or elaborated. Comprehension, assessed by 30 multiple-choice test items, was highest among subjects reading the simplified version, but not significantly better than among those reading the elaborated version. The type of modifications to the texts interacted significantly with the kind of task used to assess comprehension: replication, synthesis or inference, suggesting that different kinds of text modification facilitate different levels of comprehension

    A Generalized Options-based Approach to Mitigate Perturbations in a Maritime Security System-of-Systems

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    Due to the complex and highly dynamic contexts in which systems operate nowadays, it has become crucial that, early in the architecting phase, System Architects take into account options to be utilized throughout the system's lifecycle to improve performance and lifecycle properties, such as flexibility. This paper introduces a preliminary approach that allows for the identification of relevant options, which are capable of mitigating perturbations negatively impacting a system of interest. The approach consists of the generation, evaluation and selection of relevant generalized options (enabling both changeability and robustness), and is demonstrated by application to a Maritime Security SoS case study. The inputs to the process are a list of desired design principles to implement in the system, and a list of perturbations that may affect the delivery of value to stakeholders (options are meant to mitigate perturbations). Four different metrics for option evaluation are proposed, together with techniques that can help during the process of selection of options.Massachusetts Institute of Technology. Systems Engineering Advancement Research Initiativ

    Evaluating system change options and timing using the epoch syncopation framework

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    Complex engineering systems face many unknowns with respect to their operating contexts and time-varying stakeholder needs over their lifespan. A useful means for partitioning this problem is to consider a set of static snapshots of contexts with accompanying stakeholder needs over fixed periods of time, herein called “epochs.” Designs can be optimized towards delivering stakeholder utility in a specific epoch or across a variety of epochs. In order to consider the uncertain sequence of epochs experienced by a system, the Epoch Syncopation Framework (ESF) is introduced in this paper. This framework, using Monte Carlo analysis and Markov probability matrices, analyzes the execution of potential system “change mechanisms,” which alter a system over time to respond to epoch shifts. Through an analysis of design tradespaces, the ESF takes into account performance, schedule, cost, and uncertainty regarding experienced epoch shifts. The intended contributions of the ESF include a set of useful baseline designs, desirable change mechanisms, and strategies for executing change mechanisms across a system lifespan. The ESF is demonstrated through an application to an existing dataset containing designs for a “space tug” satellite including its set of potential epochs.Massachusetts Institute of Technology. Systems Engineering Advancement Research Initiativ

    An Empirical Investigation of System Changes to Frame Links between Design Decisions and Ilities

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    Maintaining system performance in the presence of uncertainties in design and operating environments is both challenging and increasingly essential as system lifetimes grow longer. In response to perturbations brought on by these uncertainties, such as disturbances, context shifts, and shifting stakeholder needs, systems can continue to deliver value by being either robust or changeable. These lifecycle properties, sometimes called “ilities”, have been proposed as means to achieve system value sustainment in spite of changes in contexts or needs. Intentionally designing for these lifecycle properties is an active area of research, and no consensus has formed regarding how these and other “ilities” might trade off. This paper describes ongoing research that investigates empirical examples of system changes in order to characterize these changes and to develop a categorization scheme for framing and clarifying design approaches for proactively creating ilities in a system. Example categories from the data for system changes include: the perturbation trigger for the change, the type of agent executing the system change, and the valid lifecycle phase for execution. In providing a structured means to identify system change characteristics, this paper informs future research by framing possible relationships between ilities and design choices that enable them.Massachusetts Institute of Technology. Systems Engineering Advancement Research Initiativ
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